1. Field of the Invention
In a hydrostatic drive system, it is desirable to have precise control of the engine output in both the forward and reverse directions. However, it is also desirable that the pedal controlling the output of the hydrostatic drive pumps be limited to a relatively small amount of travel. Preferably, it would be advantageous to reduce the amount of pedal travel at higher speeds while providing a greater amount of pedal travel at lower speeds so that the operator could have more precise control over the output of the hydrostatic system particularly at low speeds. It is an object of the present invention to provide a simple control mechanism associated with the output of the hydrostatic drive motor to achieve precise pedal control for the operator.
2. History of the Prior Art
Most conventional drive systems for hydrostatic front end loaders use a single hydrostatic pump and a single hydrostatic motor. This does not allow them to split the system and use half the oil for the low speed range and all of the oil for the higher speed range. Further, in a conventional system typically such operations as filling the loader bucket or digging use all of the oil available from the pump and it is very difficult to control the amount of engine horsepower used. A conventional system is constantly putting a drain on torque at high speeds and therefore operates very inefficiently. Also in a conventional system, pedal travel is directly proportional to output.
Further, in a conventional system, at higher speeds the deceleration is so fast that only by orificing the pump down to reduce pedal travel could a relatively slow rate of deceleration be produced. However, if the pump orifice is reduced, when you are accelerating you are accelerating very slowly and when you are decelerating you are decelerating very slowly. Consequently, the cycle time for the machine is considerably increased and should a front end loader be driven into a pile of dirt too hard at high speeds, the engine has a tendency to stall because the deceleration of the hydrostatic drive system is so slow that you cannot back off the hydrostatic drive pumps fast enough.